Stabilization of unsaturated carbonylic compounds



Patented Jan. 11,1938 f 2 ",1(l5,Z ,8 4.

STABILiZATION OF UNSATURATED CAR- BONYLIC ,COMPOUNDS Herbert P. A. Groll and George Hearne, Berkeley, Caliih, assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing}; Application February 24, 1936,

' Serial No. 6:5,412

4. Claims. (01. 23-250 This invention relates to the preservation and The resulting products, which comprise one orstabilization against polymerization of readily a plurality of the readily polymerizable unsatpolymerizable unsaturated organic compounds, urated carbonylic compound of the class described and it more particularly relates to a method for and a substantial amount of a phenolic compound the stabilization of readily polymerizable unsatas a polymerization inhibitor, are noveland sub- 5 urated carbonylic compounds, particularly those stantially stable compositions of matter.' Said members of thegroup of unsaturated aldehydes products may be stored for relatively long peand unsaturated carboxylic acids'which possess an riods of time and they may be shipped great disunsaturated tertiary carbon atom linked directly tances without substantial loss of material due 10 to a carbonyl group, and it also relates to the reto polymerization during storage and/ or transl0 sulting stabilized compositions. portation. The stabilized unsaturated aldehydes An object of the invention is to provide a class and/or acids alone or in admixture with other of. organic compounds which when added to readmaterials are useful raw materials in the producily polymerizable unsaturated jcarbonylic comtion of a wide variety-of valuable products, and

3 pounds, as such or in admixture with other subthey are particularly valuable raw materials in stances, will substantially retard their polymerithe production of resins, resinous materials, plaszation and/or deterioration on standing or by extics, coating compositions, etc. I posure to light, air, elevated temperatures and the A- preferred group of unsaturated carbonylic like. A further object of the inventionis to procompounds which may be effectively stabilized vide a practical and economical process for the against excessive polymerization in accordance 20 ,substantial stabilization against polymerization with the invention may be conveniently repreof members of a class of readily polymerizable unsented by the formula r saturated carbonylic compounds, which class emnr braces unsaturated aldehydes and unsaturated l I! carboxylic acids which possess an unsaturated I tertiary carbon atom linked directly to a carbonyl wherein the C carbon atom s tert a y, a 18, group of the unsaturated compound. The 'mema carbon atom linked to three carbon atoms, X bers of this class of unsaturated carbonylic comrepresents a hydro en m when the mpounds have, by virtue of'the possession of an pound is an aldehyde and ahydroxy group (OH) unsaturated tertiary carbon atom linked to ajcarwhen the compound is an acid, R represents a 30 bonyl group, such a great tendency to rapidly and hydrogen atom or a hydrocarbon radical or hysubstantially polymerize to useless polymers, drocarbon radical wherein one or more'hydrogen even under conditions normally inhibitive to the atoms have been substituted bysuitable inorganic polymerization of unsaturated compounds devoid or organic substituents, and R1 represents a hy- A of this characteristic active structure, that the drocarbon radical or a substituted hydrocarbon 35 known methods of stabilizing organic compounds radical; I

. are ineffective to inhibit'their polymerization. A subgroup of unsaturated aldehydes and un- The present invention provides a process of insaturated acids, which are particularly valuable hibitirig the polymerization of unsaturated carraw materials in the production'of useful resins 4 bonylic compounds of the class consisting of unand coating materials but which have'heretofore saturated aldehydes and unsaturated carboxylic been extremely difiicult to handledue to their acids possessing an olefinic linkage between two instability against polymerization, but which are aliphatic carbon atoms one of which is -tertiary' rendered substantially stable against,polymeriza-. and linked directly to a carbonyl group, said proction in accordance with this invention, are the ess comprising incorporating with the unsatunsaturated aldehydes and acids of the above- 5 urated carbonylic compound or compounds, by illustrated general formula wherein R represents mixing or other suitable means, a substantial a hydrogen atom; These very unstable unsatuamount of a phenolic compound, whereby the rated carbonylic compounds possess anunsatucarbonylic material is stabilized againstexcessive rated tertiary carbon atom linked by a double polymerization for relatively long periods'of time, bond to, a methene radical and by single bonds 5 to a carbon atom of a hydrocarbon radical orsubstituted hydrocarbon radical and to an aldehyde group or carboxylic acid group. Said compounds may be represented by the formula wherein the C carbon atom is tertiary, X represents a hydrogen atom or a hydroxyl group, and R1 represents a hydrocarbon radical or a hydrocarbon radical wherein one or more hydrogen atoms have been substituted by suitable inorganic or organic substituents, as halogen atoms,- carbinol groups, alkoxy groups, aralkoxy groups, aryl oxy groups, carboxylic acid groups, amino groups and the like. .For example, R and Rim the general formulas illustrated may represent alkyl radicals as' methyl, ethyl, propyl, isopropyl, butyl, isobutyl, secondary butyl, tertiary butyl, amyl, isoamyl, tertiary amyl and the like and their homologues, analogues, and substitution products; aralkyl and aryl radicals as phenyl, benzyl, naphthyl, xylyl and the like which may be substituted; alicyclic radicals as cyclopropyl,

cyclobutyl, cyclopentyl, cyclohexyl and the like as well as heterocyclic radicalsand unsaturated radicals as ethenyl, propenyl, butenyl, ethinyl, propargyl, styryl and the like and their homologues, analogues and suitable substitution'products. As examples of suitable substituted hydrocarbon radicals, R and R1 may represent radicals the methane radical in the case of the aldehydes and replacement of one of said hydrogen atoms in the case of the acids, and/or replacement of Bi by a hydrogen atom in all cases, materially decreases the tendency of the unsaturated compounds to polymerize.

The stabilization inhibitors employed in the execution of the invention are phenolic compounds. The term phenolic compound as used herein and in the appended claims embraces those organic compounds containing an aromatic radical and at least one hydroxyl group, said hydroxyl group being linked directly to a carbon atom embraced'in the nucleus of an aromatic radical. The phenolic compounds are the homologues and substitution products of the simplest member of the class, namely, phenol. A phenolic compound may be monoor poly-hydric, that is; one or more carbon atoms embraced in the same or different aromatic radicals may be linked to hydroxy groups. Other hydrogen atoms of the aromatic compound may be replaced by suitable organic oninorganic substituents.

Suitable phenolic compounds include, among others, the following: phenol, the cresols, the naphthols, the anthrols, the xylenols, cumenol, carvacrol, thymol, eugenol, catechol, resorcinol, hydroquinone, orcinol, guaiacol, phloroglucinol and the like and their homologues and analogues, as well as substitution products as the bromoand chloro-phenols, -naphthols,- -cresols, -anthrols, -xylenols, etc., chlorhydroquinone, dichlorhydroquinone, nitroso-phenol, the nitro-phenols,

etc.

Isobutenal capo-c110 and its homologues are representatives of the polymers, said polymerization reaction in general.

being irreversible. The unsaturated acid 0! the formula cape-coon resulting from the'oxidation of isobutenal, polymerizes withexplosive violence. This behavior is quite difierent from that of the-unsaturated acids not possessing this characteristic active linked directly to the aldehyde group, polymerize less readily and more slowly than those to which this invention relates. -We have also found that in the aldehydesof the-formula and in the corresponding acids of the formula the replacement of both of the hydrogen atoms of the amino-phenols, the hydroxy-diaryl ethers, the hydroxy-diary] alk-anes and the like.

The invention is not limited to the use of specific proportions of the polymerization inhibitor. In some cases, the presence oi. the phenolic compound in an amount of about 0.001% by weight of the material stabilized may be effective, in other cases, it may desirable to use as much as about 3% by weight 0 the phenolic body.

will generally be dependent upon the specific stabilizing agent, the particular compound or -mixture of compounds to be stabilized, the degree 01 stability desired, and the use to which the stabilized material is to be put. In the majority of cases, the stabilization inhibitors have the detions of from about 0.002% to about 2% by weight of the unsaturated compound or. compounds stabilized.

The phenolic compound may be added to the material in any desirable manner. The phenolic body per se may be added or lt may be added in solution or suspension in a suitable solvent. For example, the phenolic bodies may be dissolved in solvents as ethers, alcohols, etc. and the required amount of the solution added to the material to be stabilized. When a phenolic bodyper se is em- The amount of the polymerization inhibitor used sired effectiveness when employed in conc'entrain which it is dissolved or suspended. For example, although many of the above-mentioned phenolic bodies are equally effective in inhibiting polymerization of isobutenal, the cresols, pyrogallol and hydroquinone being particularly effective and of almost equal effectiveness, hydroquinone is employed in preference to the cresols and pyrogallol when discoloration is to be avoided,

for=,this compound does not cause discoloration.

When=-.discoloration is immaterial, any member @of the class of inhibitors disclosed may be used.

In accordance with the invention, the material stabilized may comprise one or a plurality of species of unsaturated aldehydes, one or a plurality of species of unsaturated acids or said material may comprise a mixture of one or more unsaturated aldehydes with one or more unsaturated acids. Mixtures of the unsaturated aldehydes and/or acids with organic solvents or diluents, with which said unsaturated compounds may be incorporated or in which said compounds may be prepared, may also be stabilized against polymerization by the addition of the required amount of a monoor poly-hydroxy aromatic body thereto. Such organic solvents or diluents include among others the aromatic and aralkyl hydrocarbons as benzene, toluene, xylene, ethyl and the saturated and unsaturated alcohols, aldehydes, ketones, ethers, esters, oxides and the like. i

To measure the rates of. polymerization of representative readilypolymerizable unsaturated aldehydes and unsaturated, acids and to demonstrate the effectiveness of representative phenolic compounds in inhibiting said polymerization, a series of tests were made, the results of which are tabulated in the following examples. It is to be understood that the examples are for illustrative purposes and that the invention is not to be regarded as limited to the specific materials stabilized or to the specific inhibiting agents therein recited.

Example I Samples of substantially the same volume were drawn from a freshly prepared stock of isobutenal, placed in glass sample bottles, and stabilized by the addition thereto of different amounts of' pyrogallol. After addition of the weighed amount of pyrogallol, the bottles were stoppered and allowed to stand, the rate of polymerization being determined by the time required for the contents of the respective bottles to solidify. The results are given in the following table for comparison, the behavior of the untreated isobutenal also being cited.

Isobutenal stabzlzzed with pyrogallol Pyrogallol Rate oi polymerization 5 5,??? Container Temperature Ega Observation None Brown glass. About 20 C 4 hours..- Murky 1 day Solid layer present 4 days- Completely solid 0.0095 Brown glass- About 20 C 1 day Clear 6days..-. Clear 13 days... Clear 47 days... Completely solid 0.01%."... Brown glass. About 20 C 1 day. Clear i 6 days.... Clear l3 deys Clear 47 days... Completely solid 0.0298....- Brown glass; About 20 C ldey.. Clear 7 days Clear 15 days--. Clear. Some flocculent matter 7 47 days... 80% solid i 77 days. Completely solid 0.0396 Brown'glass. About 20 C.-- 1 day.... Clear 7 days. Clear 15 days... Murky 47 days. Murky. No solid present. 77 day Viseags and opaque. No s 0.1050 Brown glass. About 20 C... 1 day... Cl

7deys...- 01$:

15 days-.. Clear 52 days... Very slightly murky 77 days... No change 106 days.. No change 269 days.. No change 02600..-. Brown glue. About 20 C 52 days... Clear 1 77 days... Clear 106 deysjCleer 269 days Clear None Brown glass. About C 1 hour Murky '15 hours" Completely solid 0.0500... Brown glass- About 60 C-.. 16 hours.. Clear a 40h0urs.. 50% solid Cooledtoebout 5 days.... Over 90% solid 47 days", Completely. solid 0.0493 Clear glass" In sunlight 1 day. Clear. Yellow 2 days.... Clear l 67 hours- Solid 0.0480...-... Clear glass. Diflused light" 1 day.... Clear. Yellow 15 days... Clear. Some ilocculent .material 106 days No change carbons; the hydrocarbon fractions as gasoline, kerosene, etc.; the halagenated, hydrocarbons;

The'homologues of isobutenal can be treated in substantially the same manner and stabilized against excessive polymerization for relatively long periods of time; .Other phenolic compounds may be used with comparable effectiveness, and

other proportions of the polymerization may be employed.

Example II Different samples drawn from a freshly prepared stock of isobutenal were treated with different amounts of hydroquinone and the rate of polymerization observed. The results and-conditions of the tests are given in. the following table.

The tabulated results show that hydroquinone is a very eifective agent for substantially inhibiting the polymerization of the readily polymerizable isobutenal, and that the hydroquinone is effective in widely varying concentrations.

Example III A 25 c. 0. sample of about a 50% by weight solution of the acid 1 RFC-C 0 on in benzol was placed in each of a series of brown glass sample bottles/Tueach bottle, a weighed amount-of a difierent material was added to depolymerization was observed. The results, are

shown in the following table for comparison. The

behavior of the untreated acid solution is also inhibitor and found to be desirable polymerization inhibitors when used with the acid I cups-coon (3H1 1 as well as its homologues and substitution products as phenolic compound of the group consisting of hydroquinone and pyrogallol.

2. A composition of matter comprising a compound of the formula cn, =c c0,x

wherein X is a substituent of the group consist ing of H and 0H, stabilized by the presence of from about 0.002% to 2% of a phenolic compound of the group consisting of hydroquinone and pyro'gallol.

3. The unsaturated acid of the formula CHz=(|)-COOH on, I stabilized by the presence of from about 0.002%

to about 2% of a phenolic compound of the group consisting of hydroquinone and pyrogallol.

CHl=C-COOH, CH,=-COOOH. capo-coon, CH:=C;O0OH. CH:'=CCO0H Isobutenal stabilized with hydroquinone and the like. I

' While we have described our invention in a detailed manner and provided examples illustrat- H R t P 1 m t r ydmqmnone 8 0 y ing suitable-modes of executing the same, it 18 to P 1 be understood that modifications may be made 1. cent by Container Temperature from Observation and that no vhmltamons other a weight start by the scope of the appended claims are intended.

We claim as our invention: ne B o 0 1 gay g 118; 1d 1. A composition of matter. comprising a com- 4 ays... omp ete y sci 0.0005 Brown glass. About20 0.. 13am... pound of the formula ays..- ear 15 days.. Clear orb-g-CO-x 47 days Completely solid II 00495.. Brown glass. About 20 C gays" gear 106 use. ggcgangc wherein R is a substituent of the class consisting 269 daysuni! of the methyl ethyl butyl phenyl carbinol' and 00990.. B 1 A t20C mm Cle I g 77 t; 01.35 chloromethyl groups and X is a substituent of the gag:-

group consisting of H and 011, stabilized by the 1 presence of from about 0.002% to about 2% of a 4. The unsaturated aldehyde of the formula dupe-011D H! stabilized by the presence of from about 0.002%

cited.

I hb t lit 33% Inhibit? I F to t l 1 u 24 nliorw r percen 1x nopoymerza Olllll c. c. benzol by wht. Tempomtum days soln. of acid I None About 20 C. Or'igque solid. Benzol layer on p Diphenylarnine 0.100 ..do Cleersolid. Benzollayeron top Tniocresol 0.419 Do. Propionitrile... 0.086 Opaque solid. Benzol layer on op Thiophenol 0.167 Do.

Hydroquinone. 0.111 1.06 Nosolid present Pyrogallol 0.151 1.44 Do.:

It is seen from the above table, that of the materials tested, the representative phenolic compounds, namely, pyrogallol andhydroquinone,

were the only materials effective in inhibiting the to about 2% of a phenolic compound of the group consisting of hydroqulnone and pyrogallol.

HERBERT P. A. GROLL.

GEORGE HEARNE. 

